Two Biologics Equal in RA Tx

Action Points

This study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

Note that in this study in comparing biologic agents in RA patients who had an inadequate response to methotrexate demonstrated that subcutaneous abatacept is comparable to adalimumab by most efficacy measures, including radiographic progression.

WASHINGTON -- Two biologic agents with different mechanisms of action proved equally effective in reducing the signs and symptoms of rheumatoid arthritis (RA) in a large, head-to-head, international trial, a researcher reported here.

At 12 months, the American College of Rheumatology 20% (ACR20) response criteria were met by 64.8% of patients receiving abatacept (Orencia) and 63.4% of patients on adalimumab (Humira), which was a nonsignificant difference, Michael Weinblatt said at the American College of Rheumatology.

"In the first head-to-head, fully powered trial comparing two biologics, abatacept was found to be non-inferior to adalimumab," said Weinblatt, MD, of Brigham and Women's Hospital in Boston, and colleagues.

"The availability of multiple biologic agents for the treatment of RA has created an important need for comparative assessments. Fully powered studies should provide data to rheumatologists about the relative efficacy ad tolerability of the different therapies," he said.

While post-hoc analyses have attempted to compare the efficacy of the various biologics, direct comparisons have not previously been done.

The two agents, which are both administered subcutaneously, were compared in an investigator-blinded trial termed AMPLE, which included 646 patients who had not previously received biologic therapy.

All were on background methotrexate.

The treatment regimens were 125 mg of abatacept each week or 40 mg of adalimumab every other week.

"Our hypothesis was that subcutaneous abatacept would be comparable to adalimumab with regard to efficacy in patients with RA who had an inadequate response to methotrexate," Weinblatt said.

A total of 86.2% of the abatacept group and 82% of the adalimumab group completed the first 12 months of the 2-year study.

Patients mean age was 51, 80% were white women, and mean disease duration was less than 2 years.

Baseline disease activity score was 5.5, indicating active arthritis. The mean methotrexate dose was 17.5 mg per week, and among the 50% of patients on prednisone, the mean dose was 6.4 mg per day.

By day 29 of treatment, 42.5% of the abatacept group and 47.6% of the adalimumab group had achieved ACR20 responses.

After 12 months of treatment, ACR 50% responses were seen in 46.2% and 46% of the abatacept and adalimumab groups, respectively, while ACR70 responses were seen in 29.2% and 26.2%, Weinblatt reported.

Low disease activity was achieved by 59.3% and 61.4% of the abatacept- and adalimumab-treated patients, while remission was seen in 41% of both groups.

The two groups were similar in the number of tender and swollen joints and disability scores.

The rates of radiographic non-progression during the course of the year were comparable, as were the mean changes in scores of radiographic changes, which were 0.58 and 0.38 for abatacept and adalimumab, respectively.

Overall safety was similar in the two groups, with similar rates of adverse events and serious adverse events.

However, more patients on adalimumab withdrew from the study because of adverse events (6.1% versus 3.5%), and there more patients with autoimmune adverse events in the abatacept arm (3.1% versus. 0.9%).

Injection site reactions also were more common in the adalimumab group (9.1% versus 3.8%, P=0.006).

The study is continuing for an additional 12 months, and a number of post-hoc analyses are planned, such as the potential for baseline biomarkers to be used for predicting response to the different agents.

The study was sponsored by Bristol-Myers Squibb.

Weinblatt reported receiving support and fees from Bristol-Myers Squibb and Abbott.

Reviewed by Zalman S. Agus, MD Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania

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